Patent GB-1430857-A (GB)
Title: Plastic resilient organopolysiloxane compositions
IPC: C08G77/08
Filed: 1973-12-06
Abstract: 1430857 Organopolysiloxane compositions WACKER-CHEMIE GmbH 6 Dec 1973 [6 Dec 1972] 56637/73 Heading C3T An anhydrous mixture which on exposure to water forms a plastic resilient organopolysiloxane comprises (a) a condensation catalyst which is a reaction product of a dialkyldialkoxysilane and a tin carboxylic acid salt; and (b) one or more of the following:-(i) a diorganopolysiloxane containing a "small" number of high-functional siloxane units, i.e. units of higher functionality than diorganosiloxane units, (ii) a mixture of diorganopolysiloxane and an organopolysiloxane containing or consisting of high-functional siloxane units, such that only a "small" number of high functional units are present relative to the diorganosiloxane units; (iii) a mixture of a diorganopolysiloxane and a "small" amount of a highfunctional silane, i.e. a silane of higher functionality than diorganosiloxane units. Examples of high functional siloxane units are RSiO 3 / 2  and SiO 4 / 2  units or units of the formula where R is an optionally substituted monovalent hydrocarbon radical and R<SP>1</SP> is a divalent hydrocarbon radical. The term "small" means that the number of high-functional siloxane units and the amount of high functional silane present should be such that there are 100 to 1000 diorganosiloxane units present for every uncompensated excess functionality (i.e. in excess of 2) present in the high functional siloxane units and/or silane. The diorganopolysiloxane must contain condensable groups and may contain R 3 SiO 1 / 2  units. Component. (b) preferably has a viscosity of 50-100,000 cP. at 25‹ C. Suitable silanes have the general formula R a SiX 4-a  where X is a hydrolysable group and a=0 or 1. Suitable carboxylic acid tin salts include dibutyltin diverstate (Registered Trade Mark), dibutyltin dilaurate or diacetate, di-2- ethylhexyltin maleate, bis-(dimethyl-oleyl)-distannoxane, bis - (dibutyl - lauroyl) - distannoxane, tributyltin mono-oleate and tin-2-ethylhexoate. Preferred dialkyl-dialkyloxysilanes have the formula R 2 Si(OR<SP>2</SP>) 2  where R<SP>2</SP> is a C 1 -C 18  alkyl group optionally interrupted by an ether oxygen atom. Preferably 0À1-15% wt. of (a) is used relative to (b). Optional ingredients are fillers, e.g. pyrogenic SiO 2 , TiO 2 , BaSO 4 , quartz powder, CaCO 3 , diatomaceous earth, aluminium silicate and polyvinylchloride powder; pigments, e.g. iron oxide; dyestuffs; plasticizers, e.g. long-chain carboxylic acids and triorganosiloxy - terminated diorganopolysiloxanes; lubricants, e.g. iron stearate; paraffins; scents; polyglycols. The compositions may be in a one or two component pack. In the examples, mixtures are prepared using as component (a) the reaction product of dibutyltin dilaurate or diacetate with dimethyldiethoxy silane, and as component (b) any one of the following: (1) a mixture of an OH-terminated dimethylpolysiloxane and either an Si-OH containing copolymer of CH 3 SiO 3 / 2  and (CH 3 ) 2 SiO units, or methyltriethoxysilane, or a copolymer of dimethylsiloxane units and monomethyl siloxane units, or a preheated mixture of an OH-terminated dimethylpolysiloxane and a copolymer of monomethylsiloxane, SiO 4 / 2  and dimethylsiloxane units containing Si-bonded OH and ethoxy groups; (2) an Si-OH containing copolymer of dimethylsiloxane units and monomethylsiloxane units; fillers and a trace of water. Plastic resilient compositions form after 3 days at room temperature.